The long-term objective is to develop a real-time, continuous, clinical monitor of absolute cerebral blood flow (CBF). Each year in the U.S. there are 370,000 incidents of traumatic brain injury (TBI) and 100,000 subsequent deaths. Injury results from a primary trauma and a later secondary injury caused by local ischemia (deficient blood supply) in viable tissue. Monitoring and interventional therapies to prevent secondary injury attempt to maintain an adequate level of CBF to viable tissue. While in practice CBF is not typically monitored, intracranial pressure is used to indirectly assess ischemic risk. Direct, real-time and continuous monitoring of CBF will help guide therapy, provide an early warning for ischemia, vasospasm, and neurophysiologic deterioration, allow customization of patient-specific therapy and help understand neurophysiology. In Phase I, an innovative thermal method for blood flow (perfusion) measurement will be validated in swine brain against the microsphere gold standard. This thermal technique has been validated for the measurement of blood flow in liver tissue and it holds great promise as a technique to continuously monitor patient CBF in real time. Also in the Phase I, an MRI compatible neurosurgical probe will be developed. The probe will be tested in vivo for perfusion sensitivity and for its ability to quantify small changes in tissue water content (edema). PROPOSED COMMERCIAL APPLICATIONS: Over 370,000 people in the US are hospitalized for traumatic brain injury (TBI) each year and about 100,000 deaths occur per year, nationally. The total cost associated with TBI is estimated to be $48.3 billion annually: $31.7 billion associated with hospitalization and $16.6 billion associated with fatal brain injuries. Patients with subarachnoid hemorrhage, vasospasm, brain tumors and stroke are also at risk for ischemia. The proposed low cost device to quantify blood flow continuously, in real time will have significant impact on the improved management of these critically injured patients over and above the currently used, indirect indicators of cerebral blood flow.